Constant MERGE_SLICE_NS 

pub(crate) const MERGE_SLICE_NS: i64 = _; // 300_000_000_000i64

Length of the time slices in which overlapping files are merged (300 s).

Slices start at multiples of this length since the Unix epoch, the same windows the archiver uses for its part files, so a slice of current data lines up with one file. Only one slice of rows from each overlapping file is held in memory at a time.